Re: [PATCH nft] datatype, meta: add new ifname_type for iifname/oifname

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Tue, Mar 01, 2016 at 12:00:55PM +0100, Florian Westphal wrote:
> Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> > > Ok, but how do you plan to handle the key length?
> > 
> > Right, in concatenations we can infer this from the lhs, but in set
> > definitions there is not way.
> 
> Okay.  So whats the plan there?

I would review Carlos' patches, recover Patrick patch to add typeof()
and check if we can get all the pieces together to support this.

> > What I would suggest is to recover a patch that Patrick submitted that
> > introduces typeof(X) so we can use this from set definitions. We can
> > store in the TLV the original subtype X as a string. Thus, when
> > listing back to userspace we can use this information to display back
> > the typeof(X).
> 
> So you mean you'd use something like
> 
> nft add set filter ifnames '{typeof(meta iifname); }' ?
> 
> That should indeed work since we can derive the size
> from the meta iifname (or whatever other field),
> 
> > We have to potentially support every meta and packet selector,
> > including crazy ones as 48 bits fields, and last time we discussed
> > this, we agreed that adding one type per field size is not the way to
> > go.
> 
> Ok, yes, I see your point.
> 
> > Let me know your opinion on this, thanks!
> 
> I think typeof would be good; we could indeed derive the key size with
> this without the need for a new type.

Yep, we have a plan to address this then.